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/arch/ppc64/mm/mmap.c

https://bitbucket.org/evzijst/gittest
C | 86 lines | 35 code | 10 blank | 41 comment | 9 complexity | 71226d52517962ceeeba2d961dd9c18c MD5 | raw file
 1/*
 2 *  linux/arch/ppc64/mm/mmap.c
 3 *
 4 *  flexible mmap layout support
 5 *
 6 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
 7 * All Rights Reserved.
 8 *
 9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
13 *
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17 * GNU General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
22 *
23 *
24 * Started by Ingo Molnar <mingo@elte.hu>
25 */
26
27#include <linux/personality.h>
28#include <linux/mm.h>
29
30/*
31 * Top of mmap area (just below the process stack).
32 *
33 * Leave an at least ~128 MB hole.
34 */
35#define MIN_GAP (128*1024*1024)
36#define MAX_GAP (TASK_SIZE/6*5)
37
38static inline unsigned long mmap_base(void)
39{
40	unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
41
42	if (gap < MIN_GAP)
43		gap = MIN_GAP;
44	else if (gap > MAX_GAP)
45		gap = MAX_GAP;
46
47	return TASK_SIZE - (gap & PAGE_MASK);
48}
49
50static inline int mmap_is_legacy(void)
51{
52	/*
53	 * Force standard allocation for 64 bit programs.
54	 */
55	if (!test_thread_flag(TIF_32BIT))
56		return 1;
57
58	if (current->personality & ADDR_COMPAT_LAYOUT)
59		return 1;
60
61	if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY)
62		return 1;
63
64	return sysctl_legacy_va_layout;
65}
66
67/*
68 * This function, called very early during the creation of a new
69 * process VM image, sets up which VM layout function to use:
70 */
71void arch_pick_mmap_layout(struct mm_struct *mm)
72{
73	/*
74	 * Fall back to the standard layout if the personality
75	 * bit is set, or if the expected stack growth is unlimited:
76	 */
77	if (mmap_is_legacy()) {
78		mm->mmap_base = TASK_UNMAPPED_BASE;
79		mm->get_unmapped_area = arch_get_unmapped_area;
80		mm->unmap_area = arch_unmap_area;
81	} else {
82		mm->mmap_base = mmap_base();
83		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
84		mm->unmap_area = arch_unmap_area_topdown;
85	}
86}